1. Field of the Invention
The invention relates to suction control valves and more particularly to suction control valves that vent to atmosphere residual vacuum pressure in a device to be controlled when the valve is closed.
2. Description of Related Art
Many fields use vacuum pressure or "suction", including the medical field. In the medical field, suction is typically used to remove unwanted material such as saliva or blood from a site through a suction catheter or similar device. A tube attached to a source of suction usually provides suction to the catheter. The tube has a suction control valve that controls the amount of suction provided to the catheter.
U.S. Pat. No. 3,645,497, issued to Robert P. Nyboer on Feb. 29, 1972, shows an example of a suction control valve. The Nyboer device has an elongated valve body with a longitudinal central bore extending between a first and a second end. A movable valve member is transversely and longitudinally mounted within the valve body in an arcuate channel that traverses the central bore. The valve member is made of a deformable material that allows the valve member to move longitudinally into the arcuate channel. The valve member controls the flow of materials through the valve.
As the valve member moves in the channel, the valve member moves from a position that does not obstruct the central bore to a fully closed position that totally obstructs the bore. The valve member controls the amount of suction that passes through the bore by obstructing the bore.
However, when a suction control valve such as the one disclosed in the Nyboer patent is used with a device such as a suction catheter, the ultimate distal end of the suction catheter can contact a patient's tissue. When this occurs, the vacuum pressure within the suction catheter rapidly rises to the vacuum level of the source of the vacuum pressure. This often causes the suction catheter to suck the patient's tissue into the suction catheter. Sucking the patient's tissue into the catheter may damage the tissue.
When the catheter sucks tissue into the catheter and the valve member moves into the fully closed position, a large residual vacuum pressure remains in the suction catheter between the valve member and the patient's tissue. Consequently, the patient's tissue remains drawn into the suction catheter by the residual pressure. Then, if the suction catheter is moved away from the patient's tissue, the tissue may tear. Current suction control devices do not have means for releasing this remaining vacuum pressure from the patient tissue.
Consequently, it is desirable to form a suction control valve that controls vacuum pressure while also allowing the residual vacuum pressure to vent to atmosphere. Such a suction control valve thereby allows the suction catheter to release the patient's tissue without damage to the tissue.